JPS6213891Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a parking cable guide device for a drum brake, and more particularly to a guide device that can improve the durability of the parking cable.

In one type of parking brake device, one end of a parking cable is connected to a parking lever in a drum brake, and the cable is guided by a guide part formed on the bucking plate itself or a guide member fixed to the bucking plate. There are things to do. In this case, the cable is inserted inside the compression coil spring, and the spring pushes the parking lever back to the brake non-operating position, and the cable comes into contact with the guide part or guide member (hereinafter simply referred to as the guide member) via this spring. It is widely practiced.

In this type of parking cable guide device, when a tensile force is applied to the cable during brake operation, the contact surface between the cable and the spring guided by the guide member will slide under a strong pressing force. It happens. The same applies when the cable is pulled back during the brake release operation.

By the way, since the spring has the effect of pushing back the parking lever as mentioned above,
Like a normal compression coil spring, the cable is roughly wound at a constant pitch, which increases the contact pressure on the contact surface, causing large wear on the cable and reducing its durability.

The present invention was developed against the background of the above, and an object of the present invention is to provide a parking cable guide device that can improve the durability of the cable by simple means.

The present invention is characterized by a guide portion formed on the bucking plate or a guide member fixed to the bucking plate of the compression coil spring that is fitted onto the cable and returns the parking lever to the brake non-operating position. The coil pitch of the part that contacts the cable is made smaller than the coil pitch of the other part, thereby lowering the contact surface pressure between the compression coil spring of the lever and the cable. If the contact surface pressure is lowered, wear of both the cable and the compression coil spring is reduced, and the life of the parking brake device is increased.

An embodiment of the present invention will be described in detail below with reference to the drawings.

In FIG. 1, a wheel cylinder 12, an anchor consisting of an anchor block 14 and a retainer plate 15 are fixed to a bucking plate 10, and a pair of shoe assemblies 1
6 and 18 are movably mounted by shew hold downs 20 and 22. Each shoe assembly 16, 18 is supported at one end by an anchor, and the return spring 24 is supported by the operating force of the wheel cylinder 12 at the other end.
The lining 2 is expanded against the elastic force of
6 and 28 are brought into sliding contact with the inner circumferential surface of a brake drum (not shown) to suppress its rotation.

A parking lever 34 is rotatably attached to the web 30 of one shoe assembly 16 by a pin 32, and further between the parking lever 34 and the web 30 and the web 36 of the other shoe assembly 18. A strut 38 is spanned over. The length of the strut 38 is adjusted by rotating the star wheel 40 so that the gap between the shoe assemblies 16, 18 and the inner peripheral surface of the drum can be kept constant regardless of wear of the linings 26, 28. It is being done.

One end of a parking cable 46 is connected to a cable engaging portion 44 at the free end of the parking lever 34 by a caulking fitting 48 . The other end of the parking cable 46 is connected to an operating lever inside the vehicle via an equalizer (not shown).
An outer casing 50 guides the equalizer to the bucking plate 10 of the drum brake. This outer casing 50 is the second
As shown in the figure, it is fixed to the bucking plate 10 by an outer casing end 52 attached to its end. That is, when the casing end 52 is inserted into the inside of the bucking plate 10 from the insertion hole 54 of the bucking plate,
A plurality of claws 56 formed on the casing end 52
expands outward due to its elasticity, and the end face of the claw 56 and the rubber boot 58 attached to the outer casing 50 are fixed by sandwiching the periphery of the insertion hole 54.

The parking cable 46 that has passed through the casing end 52 and entered the inside of the bucking plate 10 reaches the parking lever 34 while being guided by a compression coil spring 62 supported by a cable support 60. This compression coil spring 62 is fitted onto the parking cable 46,
It is installed with a predetermined preload between the free end of the parking lever 34 and the casing end 52, and protects the parking cable 46 from contact with other parts, as well as directing the parking lever 34 toward the non-operating position. It is energizing.

After the parking cable 46 is obliquely drawn into the backing plate 10 as shown in FIG. 2, it is supported by the cable support portion 60 and bent toward the parking lever 34. The cable support portion 60 is formed at one end of the retainer plate 15, as shown in FIG. That is, the retainer plate 15 consists of a fixed part 64 and a cable support part 60, and the fixed part 64 has a flat plate shape and has a retainer spring 66 (first
A protrusion 68 is formed for holding down the (see figure), and a mounting hole 70 is drilled.
Below the edge opposite to the protrusion 68, as shown in FIG. 4, a cable support portion 60 having an upwardly opened groove having a U-shaped cross section is connected. This cross section U
One end of the letter-shaped groove extends downward with a certain slope, and this sloped groove and the groove are connected by a gently curved surface, and the groove bottom surface of the connected portion is in the shape of an arc. The retainer plate 15 having the cable support portion 60 configured in this way is fixed to the backing plate 10 together with the anchor block 14 by rivets 72 inserted through the holes 70.

As shown in FIG. 2, a compression coil spring 62 is supported by the arcuate portion and the inclined portion of the groove bottom of the cable support portion 60, and the parking cable 46 is supported by the compression coil spring 62.
is designed so that it can move smoothly. Furthermore,
The groove bottom surface is configured such that the gap between the outer circumferential surface of the compression coil spring 62 and the groove bottom surface increases as the distance from the arc-shaped portion increases, and the action of the compression coil spring 62 that applies a biasing force to the parking lever 34. It is designed so that it does not interfere with

The coil pitch of the portion of the compression coil spring 62 supported by the cable support portion 60 is smaller than the coil pitch of other portions, and in this embodiment, the coil pitch is zero, that is, the coil pitch is tightly wound.

In the drum brake configured as described above, when a tensile force is applied to the cable 46, the parking lever 34 is rotated clockwise (in FIG. 1) around the pin 32. Then strut 3
8. The shoe assemblies 16, 18 are expanded via the shoe webs 30, 36, and the linings 26, 28 are brought into sliding contact with the brake drum to suppress its rotation.

When the cable 46 is pulled, the cable 46 slides on the inner surface of the compression coil spring 62 supported by the cable support 60 while being strongly pressed against it. However, in this embodiment, since the supported portion of the compression coil spring 62 is tightly wound, the number of turns per unit length of the compression coil spring 62 increases, and the contact area becomes larger. Contact surface pressure is low. Therefore, wear on the cable 46 is reduced and durability of the cable 46 is improved. At the same time, wear of the compression coil spring 62 itself is also reduced for the same reason.

Although one embodiment has been described in detail above, the present invention is by no means limited to this embodiment, and the present invention can be applied to cable guide devices having guide members of various shapes and arrangements, or The present invention is applied to a cable guide device including a guide portion formed by molding a part of a plate into a predetermined shape, and furthermore, a wire rod of a compression coil spring having a cross-sectional shape other than a circular shape such as a rounded quadrilateral shape. The invention can be implemented with various improvements and changes without departing from the spirit of the invention, such as using the following.

[Brief explanation of drawings]

FIG. 1 is a front view of a drum brake including an embodiment of the present invention. Figure 2 shows − in Figure 1.
FIG. FIG. 3 is a perspective view of the retainer plate 15 of the embodiment shown in FIG. FIG. 4 is a - sectional view in FIG. 1. 10: Bucking plate, 34: Parking lever, 46: Parking cable, 60: Cable support, 62: Compression coil spring.

Claims (1)

[Claims for Utility Model Registration] A parking cable that transmits brake operating force to a parking lever in a drum brake is provided through a compression coil spring that is fitted onto the cable and returns the parking lever to a non-braking position. In the parking cable guide device configured to be guided by a guide part formed on a bucking plate or a guide member fixed to the bucking plate, the compression coil spring is guided by the guide part or the guide member fixed to the bucking plate. A parking cable guide device characterized in that the coil pitch of the contacting portion is made smaller than the coil pitch of the other portion, thereby lowering the contact surface pressure between the compression coil spring and the cable.